Method for manufacturing ceramic balls for water treatment

ABSTRACT

A method for manufacturing ceramic bails for water treatment capable of exerting microbicidal activity in water and solution is provided. The method includes producing a first composition by dissolving borax (Na 2 B 4 O 7 .10H 2 O) and copper sulfate (CuSO 4 .5H 2 O) in an equivalent ratio of 1:1 to water, and drying the solution to produce a first composition, producing a second composition by adding silica to a first mixture of nitric acid and silver mixed in an equivalent ratio of 1:1 while heating the first mixture, adding more than 3 weight percents of the first composition to 200 weight percents of distilled water based on 100 weight percents of a ceramic ball while heating the distilled water, adding more than 8 weight percents of the second composition to a second mixture of the first composition and the distilled water when a total weight of the second mixture is reduced by a half, and drying the second mixture; and dehydrating the second mixture at a temperature of 400° C. to 500° C.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing ceramicballs for water treatment capable of exerting microbicidal activity inwater and solution, more particularly a method for manufacturing ceramicballs for water treatment having excellent water-purifying andwater-treating function capable of sterilizing microorganism or bacterialiving or breeding in an aqueous solution.

A variety of ceramics typically include multiple pores in its interior.The mechanical and thermal properties of the article made of the saidporous ceramics depend on the size, the shape, the porosity and thecontinuity of the pores existing inside the porous ceramics.

Particularly, the porous ceramics is used as lightweight buildingmaterials for a certain purpose, because the ceramics has theartificially formed multiple pores in its inside, and thereby renderingthe materials light and low dense. Accordingly, the demand for theceramics is largely increased in order to manufacture various filters,instruments for sintering, deodorants, heat-insulating materials,sound-proofing materials, fillers, immersing materials, flowerpot stonesand the like.

2. Description of the Related Art

In recent, as the utility value of the porous ceramics in the field ofwater-purification, filter, and the like utilizing its own absorbent anddeodorant property is increased, the development and the research forthe porous ceramics has been vigorously made. As result, a number oftechnologies for the porous ceramics have been published.

However, there has been no porous ceramics having microbicidal action initself until now. Therefore, the materials to be water-treated forsterilization were necessary to be purified with ceramics and thensubjected to a separate sterilizing process.

The object of the present invention is to provide a method formanufacturing ceramic balls for water treatment for the purpose ofsolving the above problem by rendering ceramic balls in itselfmicrobicidal activity in addition to purifying activity of ceramics, sothat microorganisms or bacteria living or breeding in an aqueoussolution may be effectively sterilized, and thus maximizing thewater-treating function.

SUMMARY OF THE INVENTION

The object of the present invention can be accomplished by providing amethod for manufacturing ceramic balls for water treatment, comprisingthoroughly dissolving borax (Na₂B₄O₇.10H₂O) and copper sulfate(CuSO₄.5H₂O) in an equivalent ratio of 1:1 to water, and then heatdrying the solution to give a product (hereafter refer to “Product A”);adding particulate silica to a separate vessel containing nitric acidand particulate silver in an equivalent ratio of 1:1 while heating todry the mixture to give a product (hereafter refer to “Product B”);adding and mixing more than 3 weight percents of Product A to 200 weightpercents of distilled water based on 100 weight percents of the ceramicballs in a separate vessel while heating; adding more than 8 weightpercents of Product B thereto when the total weight of the said mixturein the vessel is reduced by half, and heat drying the mixture; and thensufficiently dehydrating the mixture at the temperature of 400° C. to500° C.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, firstly, borax (Na₂B₄O₇.10H₂O) andcopper sulfate (CuSO₄.5H₂O) in equivalent ratio of 1:1 are thoroughlydissolved in water, and then heated to obtain Product A.

At this time, the water of crystallization bonded in borax and coppersulfate renders water solubility, and becomes an aqueous solution underthe condition of the certain temperature and the required amount ofwater with the lapse of time. Copper compound makes silver compoundeasily adhere to the sphere at the same time, since copper compound hasstrong adhesive property to the surface of other materials. Borax iscoated on the surface of them, thereby rendering coatable property.

According to the present invention, particulate silica is added tonitric acid and particulate silver in an equivalent ratio of 1:1contained in a separate vessel while heating to give a mixture. Themixture is dried by evaporation to obtain product B.

When heating the said mixture of nitric acid and particulate silver,silver nitrate is produced as shown in below Reaction Formula 1. And theproduced silver nitrate is changed to silver oxide (Ag₂O) as shown inbelow Reaction Formula 2.2HNO₃+Ag→AgNO₃+H₂O+NO₂  [Reaction Formula 1]2AgNO₃→Ag₂O+2NO₂+½O₂  [Reaction Formula 2]

The said silver oxide is again changed to ion type silver oxide underthe alkaline state as shown in below Reaction Formula 3.Ag₂O+OH⁻→AgO⁻+AgOH  [Reaction Formula 3]

The silver oxide (II) ion produced in above Reaction Formula 3 incursvariation of amino acid constituting protein of microorganism orbacteria as shown in below Reaction Formula 4 to destroy cell membraneof bacteria, thereby rendering a sterilization activity.

Particularly, since silver oxide produced in the above Reaction Formula2 is effectively adhered to ceramic balls, particulate silica is addedduring reacting nitric acid with particulate silver so as to exertingsufficient sterilizing activity.

At this time, the added particulate silica serves as a medium capable ofeffectively adhering silver compound to ceramic balls. The amount of theadded silica need not exceed the weight ratio of 2:1(w/w) to theparticulate silver. If the ratio is less than 2:0.5 (w/w), there occursa problem that cannot render sufficient sterilizing effect because theamount of particulate silver adhered to ceramic balls is small.Accordingly, it is preferable to add the said particulate silica in aratio of 2:0.5 to 2:1 (w/w) to particulate silver.

According to the present invention, in order to manufacture ceramicballs rendering silver sufficient microbicidal effect, more than 3weight percents of Product A are added to and mixed with 200 weightpercents of distilled water based on 100 weight percents of the ceramicballs in a separate vessel while heating, more than 8 weight percents ofProduct B are added thereto and mixed therewith when the total weight isreduced at least by half. The resultant mixture is dried andsufficiently dehydrated at the temperature of 400° C. to 500° C.

For the said ceramic balls, the large sands manufactured by a separatemethod as well as the ceramic spheres manufactured by various methodsmay be used. The ceramic balls are not necessary to have sphere type,and any type of the ceramic balls may be used as long as they areinorganic materials.

Product A obtained by thoroughly dissolving borax and copper sulfate ina equivalent ratio of 1:1 in water and heat drying the mixture is addedto the said ceramic balls in distilled water while heating. When theamount of Product A is less than 3 weight percents based on 100 weightpercents of the ceramic balls, there occurs a problem that the amount ofsilver compound to be adhered to the surface of ceramic balls and theamount of copper compound aiding the adhesion of silver compound to thesurface of ceramic balls are small, and thus the surfaces of theproduced ceramic balls are not smooth, and the ceramic balls can notexert microbicidal activity. Therefore, it is preferable to add not lessthan 3 weight percents, more preferably 3 to 7 weight percents ofProduct A, based on 100 weight percents of ceramic balls. When theamount exceeds 7 weight percents, the large amount of copper compound isremained unadhered.

When the mixture obtained as above is heated until the volume is reducedby more than half of the total weight by evaporation of water, Product Bobtained by adding nitric acid and particulate silver in a equivalentratio of 1:1 to particulate silica and evaporating and drying is added.When the amount of Product B is less than 8 weight percents, thereoccurs a problem that the amount of silver compound adhered to ceramicballs is small, the surfaces of the resultant ceramic balls are notsmooth, and thus the ceramic balls can not exert microbicidal activity.Therefore, it is preferable to add not less than 8 weight percents, morepreferable 8 to 15 weight percents of Product B, based on 100 weightpercents of ceramic balls. When the amount exceeds 15 weight percents,silver compound remained after being adhered, is adhered to ceramicballs and there causes unnecessary costs.

The ceramic balls having microbicidal activity according to the presentinvention can be manufactured by adding Products A and B to distilledwater, drying and sufficiently dehydrating the mixture at thetemperature of 400 to 500° C.

The said dehydrating temperature needs to remove the water ofcrystallization bonded to borax and copper sulfate. When the water ofcrystallization is removed from borax and copper sulfate adhered toceramic balls at the said temperature, the borax and copper sulfatecompound is present in ceramic balls in a water-insoluble state.

A microbicidal activity is presented according to the above ReactionFormulae 1 to 4, since silver nitrate has stability in the state that itis simultaneously adhered to copper compound and a very slight amount ofsilver nitrate is melted to an aqueous solution.

The present invention is described in more detail by Examples andComparative Examples, but the Examples are only illustrative and,therefore, not intended to limit the scope of the present invention.

EXAMPLES Examples 1 to 5

Borax and copper sulfate (CuSO₄.5H₂O) in an equivalent ratio of 1:1 arethoroughly decomposed in water, and heat dried to obtain Product A.Nitric acid and particulate silver in an equivalent ratio of 1:1 arecharged in a separate vessel. Particulate silica is added thereto in anequivalent ratio of 2:1 (w/w) to the said particulate silver, andvaporized and dried to obtain Product B.

The said Product A is charged in a separate vessel containing 200 g ofceramic balls and 400 g of distilled water while heating in theproportion shown in Table 1 as below and is mixed. When the total weightis reduced by half, the said Product B is added thereto in theproportion shown in below Table 1, dried and sufficiently dehydrated atthe temperature of 500° C. to produce ceramic balls having microbicidalactivity. The condition of the resultant ceramic balls' surfaces arevisually observed and the result is shown in below Table 1:

TABLE 1 Amount of Amount of Condition Product A (g) Product B (g) ofSurface Example 1 2 22 X Example 2 6 22 ⊚ Example 3 10 22 ⊚ Example 4 1010 X Example 5 10 16 ⊚ ⊚: smooth and glossy ◯: glossy, but not smooth X:not glossy nor smooth.

As is apparent in Table 1, when it was confirmed that the surface ofceramic balls is smooth and glossy when Product A is used in the rangeof the present invention in Examples 2 and 3, provided that Product B isused in same amount as 22 g in Examples 1 to 3. Meanwhile, the surfaceof ceramic balls is not glossy and smooth when the amount of Product Ais less than the lower limit of the present invention in Example 1. Thequality of the ceramic balls obtained in Example 1 is not good.

The reasons why the said result is obtained are that the surface ofceramic balls is glossy and smooth in case that silver compound adheredto ceramic balls is more than a certain amount, and that the surface ofceramic balls is not glossy and smooth in case that silver compoundadhered to ceramic balls is small.

When it was also confirmed that the surface of ceramic balls is notsmooth and glossy when Product B is used in an amount of less than therange of the present invention in Example 4, but the surface of ceramicballs is smooth and glossy when the amount of Product B is used inwithin the range of the present invention in Example 5, provided thatProduct B is used in amounts of 10 g and 16 g in Examples 4 and 5,respectively.

The reasons why the said result is obtained are that the surface ofceramic balls is glossy and smooth in case that a certain amount ofsilver compound is adhered to ceramic balls, and that the surface ofceramic balls is not glossy and smooth in case that silver compoundadhered to ceramic balls is less than a certain amount, and thus theamount of the adhered silver compound is small.

On the basis of the said obtained result, an experiment forsterilization activity was commenced ad follows by using ceramic ballshaving smooth surface manufactured in Example 3.

<Experiment>

160 g of ceramic balls manufactured as above were charged in a vessel,500 ml of purified water were added thereto, and then sterilized withhigh pressured vapor at the temperature of 121° C. for 15 minutes. 0.5mlof buoyant (107 CFU/ml) of strain (Legionella Pneumophila: GIFU 9134)incubated at the temperature of 37° C. for 5 days with agar medium flatplate is added to the vessel, and then shaken. The vessel iscontinuously shaken for 3 minutes after adding the buoyant of strain.The contents in the vessel are stirred at an interval of 20 seconds for5 minutes, at an interval of 30 seconds for 30 minutes, and at aninterval of 30 minutes for 12 hours, respectively.

1 ml of the said reacted liquid was taken as a sample at every interval,and was diluted with the sterilized and purified water. The number ofliving bacteria (CFU) per 1 ml of the reacted liquid was counted byusing an agar medium flat plate.

TABLE 2 Number of Living Bacteria initial time 3 min. 5 min 30 min. 1hr. 3 hrs. 6 hrs. 12 hrs. Exp. 2.3 × 10⁵ 1.2 × 10⁵ 2.4 × 10⁴ 3.2 × 10³2.8 × 10³ 2.6 × 10³ 2.3 × 10² 9

As is apparent in Table 2, as result of an experiment for sterilizationby using ceramic balls manufactured by the present invention, it wasconfirmed that the bacteria are rapidly reduced with the lapse of time,and that the number of living bacteria is less than 10 after 12 hours.

As described above, the present invention provides a method formanufacturing ceramic balls for water-treatment capable of exertingexcellent microbicidal activity in water solution, by coating a compoundhaving a microbicidal activity to ceramic balls, thereby renderingceramic balls microbicidal.

1. A method for manufacturing ceramic balls for water treatment,comprising the steps of: (a) thoroughly dissolving borax (Na₂B₄O₇.10H₂O)and copper sulfate (CuSO₄.5H₂O) in an equivalent ratio of 1:1 in water,and drying the solution in accordance with a heating process, to preparea first composition (A); (b) mixing nitric acid and particulate silverin an equivalent ratio of 1:1, adding particulate silica to the mixtureof nitric acid and particulate silver under a heating condition, toprepare a second mixture, and drying the second mixture in accordancewith an evaporation process, to prepare a second composition (B); (c)adding 200 parts by weight of distilled water to 100 parts by weight ofspherical ceramic bodies, to prepare a third mixture, adding more than 3parts by weight of the first composition (A) to the third mixture undera heating condition, to prepare a fourth mixture, and heating the fourthmixture until the total weight of the fourth mixture is reduced by half;(d) adding more than 8 parts by weight of the second composition (B) tothe weight-reduced fourth mixture, to prepare a fifth mixture, anddrying the fifth mixture, to obtain ceramic balls coated with the firstcomposition (A) and the second composition (B); and (e) sufficientlydehydrating the ceramic balls at a temperature of 400° C. to 500° C. 2.The method according to claim 1, wherein the particulate silica is addedat the step (b) in a weight ratio of 2:0.5 to 2:1 (w/w) with respect tothe particulate silver.
 3. The method according to claim 2, wherein thefirst composition (A) is added at the step (c) in an amount of 3 to 7weight percentages based on 100 weight percentages of the ceramic balls.4. The method according to claim 3, wherein the second composition (B)is added at the step (d) in amount of 8 to 15 weight percentages basedon 100 weight percentages of the ceramic balls.
 5. The method accordingto claim 1, wherein the first composition (A) is added at the step (c)in an amount of 3 to 7 weight percentages based on 100 weightpercentages of the ceramic balls.